While genetic influences are important to understanding obesity, they cannot explain the current dramatic increase seen within specific countries or globally. It is accepted that calorie consumption in excess of calorie expenditure leads to obesity; however, what has caused shifts in these two factors on a global scale is much debated.
Social class
The correlation between social class and body mass index (BMI) varies globally. A review in 1989 found that in developed countries women of a high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity. An update of this review carried out in 2007 found the same relationships, but they were weaker. The decrease in strength of correlation was felt to be due to the effects of globalization. Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for physical fitness. In undeveloped countries the ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns. Attitudes toward body mass held by people in one's life may also play a role in obesity. A correlation in BMI changes over time has been found between friends, siblings, and spouses.
Food deserts The term "food desert" was reputedly first used by a resident of a public sector housing scheme in the west of Scotland in the early 1990s to capture the experience of living in a deprived neighborhood where food was expensive and relatively unobtainable. The phrase first appeared in an "official" publication in 1995, as part of a report from a policy working group investigating grocery distribution and food retailing on behalf of the Low Income Project Team of the UK government's Nutrition Task Force. The term "food desert" is used to "describe populated urban areas where residents do not have access to an affordable and healthy diet." Reports have "suggested that food deserts may damage public health by restricting the availability and affordability of foods that form the components of a healthy diet." Nicole I. Larson and her colleagues did a research review to relate obesity with neighborhood environments. They argue that "availability of fast-food restaurants and energy-dense foods has been found to be greater in lower-income and minority neighborhoods." When neighborhoods have more access to supermarkets with fresh produce there is a decrease in unhealthy dietary habits and levels of obesity. "Low-income, minority, and rural neighborhoods" are affected the most by this little access to supermarkets and tend to have greater access to fast-food restaurants and convenience stores with energy-dense food. For example, one study found that high-poverty areas and all African American areas (regardless of income) were less likely than predominantly white higher-income communities to have access to foods that enable individuals to make healthy choices. However, some recent studies have not been able to confirm the claims that distance to supermarkets predicts obesity or even diet quality.
Stress Stress and emotional brain networks foster eating behaviors that may lead to obesity. The neural networks underlying the complex interactions among stressors, body, brain and food intake are now better understood. Stressors, by activating a neural stress-response network, bias cognition toward increased emotional activity and degraded executive function. This causes formed habits to be used rather than a cognitive appraisal of responses. Stress also induces secretion of both glucocorticoids, which increases motivation for food, and insulin. Pleasurable feeding then reduces activity in the stress-response network, reinforcing the feeding habit. One study found that "higher work stress was associated with higher consumption of specific fatty foods among men but not women." In another study done by Richardson and her colleagues, "a sample of low-income women with children, we found that perceived stress was directly and positively associated with severe obesity, independent of eating behaviors and diet quality. In addition, perceived stress was directly and positively associated with unhealthy eating behaviors."
Education A study done by Shaikh and colleagues found that "in both unadjusted and adjusted analyses, lower levels of education and incomes were generally associated with higher likelihood of obesity and higher mean BMI." Shaikh and his colleagues gathered data from the US National Health Interview Survey about 23,434 adults. With that information, the researchers conducted regression analyses to depict obesity in relation to different socioeconomic parts, such as education. With a P value <.001, they found that obesity was less common in adults with a higher educational attainment versus those with a lower educational attainment. They concluded that education and obesity are highly associated and their call to action was for public schools to have more health education. Similarly, in a study done in Germany, researchers found that "indicators of parental education were most strongly associated with children's obesity. There was a strong dose–response relationship between a composed index of social class and obesity. Children of the lowest social status had a more than three-fold risk to be obese than children of the highest social status in the screening population."
Social context of meals
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